Here are some concerns gardeners have this time of year.
Q: Is it true letting grass grow against the trunks of trees slows their growth?
A: Yes. Grass roots produce chemical inhibitors that slow tree growth. In the beginning, keep grass at least a foot from the trunk. As the tree grows, expand the grass-free area out. You’ll also find you can’t injure the tree with your weed whip.
Q: Why did our vincas (periwinkles) die? They also died last year.
A: Vincas are very susceptible to Phytophthora and Rhizoctonia. Both are soil-borne fungi that thrive if plants are grown in overly moist soil conditions. When we see plants wilting, we want to give them more water, and it makes matters even worse as plants die even faster. These diseases persist for months in our soils. If your vincas died, don’t plant them in that area for at least two years. Other annuals such as marigolds are more tolerant.
Q: How do I prune hibiscus plants?
A: Hibiscus bring a tropical atmosphere to landscapes with its mammoth (2 inches to 3 inches in diameter) summer flowers. It doesn’t take much pruning to keep them compact. In the early spring, cut back on last season’s growth but keep several buds as potential flowering sites. The best hibiscus plants I see have low-growing bushes under them. The added humidity helps plants produce more flowers.
Q: We are converting our lawn into a desert landscape and know the shrubs we want to use but are stumped about a tree to plant. We like mesquites. What should we use?
A: Plant a Texas honey mesquite. I consider it one of the best for landscapes. Its glossy, fine-textured, fernlike, leaves hang on flexible twigs making it a welcoming attraction to catch summer breezes. You can train it into a multitrunked or single-trunked picturesque tree you’ll love.
Q: Why didn’t my broccoli seeds germinate?
A: I suspect you planted them too deep. In the spring, lay seeds on the soil and lightly cover them with mulch and keep it moist.
Or, you are dealing with old seeds, which slows down germination. To test for germination, place 10 seeds in paper towels and roll them up, place in a glass with some moisture in the bottom and let them capillary up to moisten seeds. After a week, count the germinating seeds. If only a few seeds germinate, you had old seeds. Get new ones.
Q: Why don’t my pyracanthas have berries this year? I carefully manicured them into a hedge.
A: Keeping the hedge “manicured,” you removed the flowering wood. Pyracanthas produce berries on last year’s growth. Avoid removing the new shoots to produce the berries.
Q: When and how do I plant cannas my neighbor gave me?
A: Plant them anytime in a rich, well-drained soil. They respond best to an eastern exposure. In the spring, as they start growing, feed them to keep them lush and vigorous. Next fall, after a frost, cut them back to the ground. In a few years you’ll be giving bulbs away.
Q: How do you get rid of black widow spiders organically?
A: Spiders in your home are a signal that you have insects — they’re the main diet for spiders. Black widow spiders work from a web in secluded places. Clean up these areas and your problem will disappear or use permethrin sold by most nurseries to control them.
Q: We want to get rid of our cat’s claw but it keeps coming back. How can I get rid of it without using herbicides?
A: The best way is to dig out the stump. Another way is to mulch over it so light can’t reach the plant’s crown. Excluding light dissipates the energy within the plant and it dies.
Q: Are mushrooms (fungus) dangerous?
A: Fungus is a natural part of our ecosystem. Fungi are the cleanup crews of landscapes, breaking down organic material into nutrients for plant use. Most of the time, you never notice fungi except when mushrooms appear. Fungi are prevalent in your soils. As long as you don’t overwater, they seldom affect plants. If mushrooms do appear, get rid of them as some are poisonous.
Q: Is alfalfa hay OK to use with our kitchen scraps in composting?
A: It’s an excellent component to add to your compost. It also introduces nitrogen, something microorganisms need to compost faster.
Linn Mills’ garden column appears on Sundays. You can reached him at email@example.com or call him at 702-526-1495.